Mechanical and stratigraphic constraints on the evolution of faulting at Elk Hills, California

Abstract

To unravel the four-dimensional evolution of the Elk Hills oil field, Kern County, California, we integrated seismically interpreted fault surfaces, stratigraphic units, and stratigraphic features with mechanical models. Correspondence of synthetic stratigraphic surfaces, deformed by modeled vertical-displacement fields, to seismically interpreted stratigraphic surfaces represented on structure contour maps suggests that the tectonic history described here is structurally, stratigraphically, and mechanically consistent, placing constraints on the regional deformation mechanism and local structure. During the period investigated, middle Miocene to present, the eastern and the western parts of the Elk Hills anticline developed in response to a regional horizontal shortening oriented at about 35. The apparent bend in the trend of the anticline, from northwest-southeast in the western part of the field to east-west in the eastern part of the field, is generated by the intersection of two distinct fault systems. In both fault systems, north-dipping fault surfaces are backthrusts of older south-dipping faults. These results have direct implications for the migration and emplacement of hydrocarbons at Elk Hills, suggesting that the upper Miocene Stevens turbidite oil pools were derived from sources to the south. Additionally, this study indicates that the method by which stratigraphic and structural interpretations are incorporated into a sequence of forward mechanical models represents an effective means of constraining the structural evolution of a fault network that developed within a syndepositional tectonic setting.